Zhang L, Yu Y, Mackin S, Weight F F, Uhl G R, Wang J B
Laboratory of Molecular and Cellular Neurobiology, National Institute on Alcohol Abuse and Alcoholism, Bethesda, Maryland 20892-8205, USA.
J Biol Chem. 1996 May 10;271(19):11449-54. doi: 10.1074/jbc.271.19.11449.
mu opiate receptors, the principal sites for opiate analgesia and reward, can display compensatory responses to opiate agonist drug administration. Agonist-induced K+ channel responses mediated by these receptors desensitize when examined in Xenopus oocyte expression systems. Mechanisms underlying such processes could include phosphorylation events similar to those reported to desensitize other G-protein-linked receptors. We used C-terminally directed anti-mu receptor antibodies to immunoprecipitate a phosphoprotein with size appropriate for the mu receptor from stably expressing Chinese hamster ovary cells. Phosphorylation of this mu opiate receptor protein was enhanced approximately 5-fold by treatment with the mu agonist morphine. The time course and dose-response relationships between mu receptor phosphorylation and agonist-induced desensitization display interesting parallels. Phosphorylation of mu opiate receptor protein is also enhanced approximately 5-fold by treatment with the protein kinase C activator phorbol 12-myristate 13-acetate. The protein kinase inhibitor staurosporine blocked the effect of phorbol 12-myristate 13-acetate on mu receptor phosphorylation. However, staurosporine failed to block morphine-induced phosphorylation. These observations suggest that several biochemical pathways can lead to mu receptor phosphorylation events that may include mechanisms involved in mu receptor desensitization.
μ阿片受体是阿片类镇痛和奖赏的主要位点，对阿片类激动剂药物给药可表现出代偿反应。在非洲爪蟾卵母细胞表达系统中检测时，由这些受体介导的激动剂诱导的钾通道反应会脱敏。此类过程的潜在机制可能包括与使其他G蛋白偶联受体脱敏的报道相似的磷酸化事件。我们使用C端定向抗μ受体抗体从稳定表达的中国仓鼠卵巢细胞中免疫沉淀出一种大小与μ受体合适的磷蛋白。用μ激动剂吗啡处理后，这种μ阿片受体蛋白的磷酸化增强了约5倍。μ受体磷酸化与激动剂诱导的脱敏之间的时间进程和剂量反应关系显示出有趣的相似性。用蛋白激酶C激活剂佛波醇12-肉豆蔻酸酯13-乙酸酯处理后，μ阿片受体蛋白的磷酸化也增强了约5倍。蛋白激酶抑制剂星形孢菌素阻断了佛波醇12-肉豆蔻酸酯13-乙酸酯对μ受体磷酸化的作用。然而，星形孢菌素未能阻断吗啡诱导的磷酸化。这些观察结果表明，几种生化途径可导致μ受体磷酸化事件，这可能包括参与μ受体脱敏的机制。
